Although the term "target" does not necessarily denote an object or location pinpointed by an attacker, the determination of such a distance is of primary interest in the field of so-called electronic warfare in which a missile of the type known as surface-to-air laser-guided projectile (SALGP) is aimed at a tank, a naval vessel or some other weapons carrier. Devices are already known for determining the relative position of an observation platform or post and a laser-illuminated area. Two such devices, manufactured in the United States, bear the designations LAHAWS (made by Fairchild Camera and Instrument Corp.) and AM/AVR-2 (made by Perkin-Elmer Corp.). As far as I am aware, however, no system exists for determining the distance of the illuminated area from the observation platform or post.
The knowledge of that distance would be significant in actual warfare in order that an operator of the threatened target may be alerted to the danger in time for taking effective countermeasures such as evasive movements or the generation of a smoke-screen. Conversely, this type of information can be used in a feedback loop from a forward point to correct the aim of a laser beam.